The invention relates generally to vehicles used to move aircraft on the ground, and more particularly to moving aircraft having a double wheel.
It is desirable to provide a transfer device that grips a double, and which is intended to move an aircraft or other device equipped with double wheels on a base, and which transfer device includes a fork-shaped frame and pairs of rollers located on each of the prongs of the fork and devices to revolve the rollers and devices to compress them, both pairs of rollers being able to be placed from the side in front and behind the wheel of the device to be moved, and in which by means of rotating the rollers pressed against the wheel, the wheel of the device to be moved is made to revolve and the entire device to move.
Here a double wheel also means the adjacent wheels of the wheels of a bogie. The transfer device is mainly intended to move passenger aircraft at an airport. Here the compression and friction rollers also mean sets of rollers formed by more than one roller close together. A track or similar apparatus may be used on top of the set of rollers.
The structure of a transfer device can be considerably lightened when the rotational force is transferred to the aircraft's own wheel from the operating wheels or friction rollers that form part of the transfer device. An entirely universally applicable light transfer device's construction is shown in Finnish Patent Application FI 833275 (partly corresponding to W085/01265). This requires no contact with the bogie of the aircraft in order to press the drive wheel against the wheel of the aircraft. The compression is achieved by means of the mutual movement of the pressure rollers, connected by an intermediate device, which are placed around the wheel of the aircraft.
A transfer device, which grips a double wheel, especially the front undercarriage bogie of an aircraft, is shown in U.S. Pat. No. 3,005,510. In it the neighbouring bogie wheels are used by means of two friction tracks, which are wedged between consecutive bogie wheels. In the known transfer devices that grip double wheels the problem is that they can only be used with some types of aircraft. The dimensions of double wheels in different aircraft vary greatly. The smallest wheel sizes have a diameter of only 80 cm, whereas the largest diameter is a large as 2 m. An even greater problem than this is the wide range of dimensions between the wheels. In the smallest aircraft the distance between the tracks of the wheels is only 80 cm and in the largest 1400 cm. In this case a transfer device with a U-shaped frame must be made very wide and the lateral adjustment of the rollers very long. Transfer devices with a U-frame are shown in, among others, WO publications 87/06542 (PCT/FI87/53).